1. Field
The present invention relates to a drive mechanism that converts a force supplied from an operator or other means along a complex curve path into rotary motion. More particularly, the present invention relates to a cyclodial drive mechanism configured for an operator driven or motor driven exercise apparatus such as a stationary bicycle, recumbent stationary bicycle, cross trainer or other devices.
2. State of the Art
The benefits of regular exercise to improve overall health, appearance and longevity are well documented in the literature. For exercise enthusiasts, the search continues for safe apparatus that provides exercise for maximum benefit in minimum time with less boredom.
Exercise bikes currently use simple cranks to guide the feet along a circular path while receiving operator force to rotate a flywheel. Several attempts have been made to guide the feet along an elliptical path while seated for exercise such as Eschenbach in U.S. Pat. No. 5,836,855 and Maresh in U.S. Pat. No. 5,938,570. Knudsen in U.S. Pat. No. 5,433,680 shows an elliptical path generating mechanism with pedals having only one pivot allowing the pedal to rotate unconstrained about the pivot as in a bicycle crank. Marchou in U.S. Pat. No. 2,088,332 shows a gear pair configured to receive force from a piston. Stiller et al. in U.S. Pat. No. 5,419,572 shows a pair of gear stacks used to guide foot pedals along an elliptical path for a bicycle.
Recently, a new category of exercise equipment has appeared on the commercial market called elliptical cross trainers. These cross trainers guide the feet along a generally elliptical shaped curves to simulate the motions of jogging and climbing. Several commercial cross trainers are now offered with elliptical foot movement that be changed when desired by an operator.
Cyclodial curves such as the Three Leaved Rose and Four Leaved Rose can be generated by mathematical formulas as shown on page 426 in CRC Standard Mathematical Tables published by the Chemical Rubber Publishing Company. Spiral curves are given on page 423 of the same book. Segasby in U.S. Pat. No. 6,334,836 shows a gear pair to guide a foot pedal along an ellipse, circle or straight line depending upon where the pedal is attached to the planet gear. The sun gear to planet gear ratio is 2/1. Several dead spots occur with this embodiment where the pedal is unable to accept force from the foot during a portion of the cycle. Chuang in U.S. Pat. No. 5,833,583 offers an improvement in a drive mechanism intended to guide the foot along an elliptical path using a gear pair and a slideable foot support. The slideable foot support helps to overcome the dead spots along an elliptical path as seen in the Segasby device. However, it is difficult in practice to guide a slideable member without clearance problems over extended use.
There is a need for a drive mechanism to guide a pedal, foot support, connector link or handle along a cyclodial curve without slideable members. There is a further need for a cyclodial drive mechanism that can be incorporated in an exercise apparatus or other device where the drive pivot such as a pedal follows a cyclodial curve having more than two leaves or lobes as seen with elliptical curves. There is a further need for a drive mechanism that changes radius on a periodic basis.
It is one objective of this invention to provide a cyclodial drive that converts complex pedal movements into rotary motion. Another objective of this invention is to integrate the cyclodial drive into several exercise apparatus. Yet another object of this invention is to provide cyclodial curves for exercise having multiple leaves or lobes.
The present invention relates to the kinematic motion control of pedals which follow more complex curves having two or more lobes and spirals. More particularly, a cyclodial drive mechanism based upon a linkage and gear pair can be incorporated into several exercise apparatus to drive a flywheel.
In the preferred embodiment, a pair of circular sun discs are fixed to a frame. Planet discs are configured to orbit the sun discs with rotation determined by the sun/planet size ratio. The rotary movement of the planet disc is converted into cyclodial movement by a linkage pivotally connected to the planet disc. When the sun/planet size ratio equals two, elliptical type curves result having two lobes. These cyclodial curves are centered about the center of the sun disc. When the size ratio does not equal two, more complex cyclodial curves result having more than two lobes or spirals.
A crank is rotatably connected to the center of the sun disc and supports the planet disc at a pivot. The sun disc and planet disc can be coupled as a gear pair or by a timing belt, chain or other means. When a pair of spur gears are used with teeth engaged, the planet rotates in the same direction as the crank. The introduction of an idler gear between the sun gear and planet gear, where the sun and planet gear teeth are engaged only by the idler gear, will cause the planet gear to rotate opposite in direction to the crank. The use of a timing belt or chain to engage the teeth will also cause the planet gear to rotate opposite the crank. A pair of sun discs, planet discs and cranks will usually be needed for an exercise apparatus using two pedals. In some cases, a linkage or gear turnaround can be used in lieu of the second cyclodial drive.
A pair of cranks are connected to a crankshaft that passes through each sun disc. A loading pulley or sprocket is attached to the crankshaft between the sun discs to drive a flywheel or other apparatus. Alternately, a motor engaged with the loading pulley or sprocket can drive the cyclodial drive to be used as a passive exercise apparatus or other device. Attached to each planet disc is a relatively short planet link that rotates with the planet disc. A rocker link is pivotally connected to each crank distal the planet gear. A pair of coupler links are pivotally connected to the planet links and rocker links. The crank, planet link, rocker link and coupler link form a linkage which is connected to the planet disc and crankshaft. Each coupler link is extended to provide driving force input/output for a drive pivot from a pedal, foot support member, arm lever, handle or other means of force application.
A first application of the cyclodial drive described above, would be to a stationary exercise bike having a seat located generally above the cyclodial drives and with a handle for the arms. Pedals would be connected at the drive pivot for the feet of the operator to supply the driving force directly to the driving pivots. A flywheel would be coupled to the loading pulley with a timing belt along with some form of load resistance.
A second application would be similar to the first application except the seat is closer to the floor to form a recumbent bike.
A third application would have a pair of foot support members pivotally connected to the drive pivots and to a pair of guides to form a cross trainer. The guides can take many forms such as a rocker link, roller and track or other guide linkage. Pedals would be attached to the foot support members. Arm exercise can also be coordinated with the foot support movement. The cyclodial curve generated by the cyclodial drive would be modified at the pedal, in the form of a height reduction or concentric ellipses with a spiral cyclodial curve.
A fourth application has a pair of arm levers pivoted to a frame and pivotally connected to the drive pivots with a pair of connector links. A back and forth hand movement drives the cyclodial drive. The hand stroke will vary according to the choice of sun/planet size ratio. Foot supports can be added to the arm levers. The drive pivot dwells at a minimum radius from the crankshaft then increases to dwell at a maximum radius. The sequence continues as the crank rotates.
A fifth application is intended for arm exercise only where a pair of handles are pivotally connected to the drive pivots. Again a flywheel and load resistance would be driven by the cyclodial drive. The operator can be seated or standing.
Alternately, a motor can be attached to any of the applications to drive the cyclodial drive for a passive system to rehabilitate the arms and legs or other usage. Other forms of load resistance such as friction discs, magnetic, air, friction belt, etc. may also be used.
In summary, this invention provides the user with a cyclodial drive that can be incorporated into a variety of exercise apparatus or other devices. The cyclodial drive can have a number of different cyclodial curve paths depending upon the sun/planet size ratio. Cyclodial curves with multiple lobes or spirals produce a different pedal movement for each lobe traversed by the pedal to reduce the boredom of exercise and to exercise different muscles.